Hydrate the suppressor and use it as usual.
Delivering eluent without hydrating the suppressor may cause sodium ion to enter a section from which the ion is hard to remove, resulting in a large negative drift.
(For ICDS-40A) Temporarily increase the suppressor current to 200 mA and check the drift. If this eliminates the drift, then clean the suppressor with sulfuric acid.
Click here for Rinsing the Suppressor with Sulfuric (Regeneration Procedure).